Lamp base



FIG. 1 is a perspective view of the lamp base.

FIG. 2 is a front elevational view of the lamp base, the rear, left side,and right side elevational views being identical.

FIG. 3 is a top plan view of the lamp base; and,

FIG. 4 is a bottom plan view of the lamp base.

Broken lines illustrate features or environmental components that are not part of the design sought to be patented. 

I claim the ornamental design for a lamp base, as shown and described. 